Self aligned symmetric intrinsic process and device

Abstract

A semiconductor device and method of fabricating the device. An emitter region is formed self centered and self aligned symmetrically with a base region. Using frontside processing techniques, a collector is formed symmetrically self-aligned with the base region and the emitter region. The collector region may be further formed self-centered with the base region using backside processing techniques. The self-aligned and self-centered symmetric structure virtually eliminates parasitic elements in the device significantly improving the device performance. The device is scalable on the order of approximately 0.1 microns. The method also provides reproduceability and repeatability of device characteristics necessary for commercial manufacture of the symmetric device.

What is claimed as new and desired to be protected by Letters Patent is:  
     
       1. A semiconductor device, comprising: 
       a first active region having a first portion with a first width and a second portion with a second width smaller than said first width;  
       a second active region having a third portion with a width substantially the same as said first width and fourth portion with a width smaller than said first width;  
       a third active region disposed between said first and second active regions having a width substantially the same as said first width; and  
       first, second and third contacts connected respectively to said first, second and third active regions.  
     
     
       2. A device as recited in  claim 1 , comprising: 
       one of said first and second active regions being self-centered with said third active region.  
     
     
       3. A device as recited in  claim 1 , wherein: 
       said first active region comprises an emitter;  
       said second active region comprises a collector;  
       said third active region comprises a base; and  
       said collector is symmetrically self-aligned with said emitter.  
     
     
       4. A device as recited in  claim 3 , comprising: 
       one of said collector and said emitter being self-centered with said base.  
     
     
       5. A device as recited in  claim 3 , comprising: 
       said emitter having said second portion self-centered with said base; and  
       said collector having said fourth portion self-centered with said base and symmetric with said second portion.  
     
     
       6. A device as recited in  claim 3 , comprising: 
       said base having a lower and an upper ledge; and  
       said third contact comprising:  
       a first base contact formed on said upper ledge self-aligned with said emitter; and  
       a second base contact formed on said lower ledge self-aligned with said collector.  
     
     
       7. A device as recited in  claim 3 ; comprising: 
       said base having a ledge;  
       said third contact formed on said ledge self-aligned with said emitter.  
     
     
       8. A device as recited in  claim 7 , wherein: 
       said base has ledges on opposing sides; and  
       said third contact comprises:  
       a first base contact formed from a front side of said device; and  
       a second base contact formed opposing said first base contact on said ledge self-aligned with said collector and formed from a back side of said device.  
     
     
       9. A device as recited in  claim 3 , wherein: 
       said device is a heterojunction bipolar transistor.  
     
     
       10. A device as recited in  claim 3 , wherein: 
       said base layer has a lower ledge and an upper ledge; and  
       said third contact comprises:  
       a first base contact formed on said upper ledge; and  
       a second base contact formed on said lower ledge.  
     
     
       11. A device as recited in  claim 1 , comprising: 
       said second portion disposed between said third active region and said first portion.  
     
     
       12. A device as recited in  claim 1 , comprising: 
       said fourth portion disposed between said third active region and said third portion.  
     
     
       13. A semiconductor device structure, comprising: 
       a first active region having a first portion with a first width and a second portion with a second width smaller than said first width;  
       a second active region having a third portion with a width substantially the same as said first width and fourth portion with a width smaller than said first width;  
       a third active region disposed between said first and second active regions having a width substantially the same as said first width; and  
       first, second and third contacts connected respectively to said first, second and third active regions.  
     
     
       14. A structure as recited in  claim 13 , wherein: 
       a position of said first active region in said structure is self-centered with a position of said third active region; and  
       a position of said second active region in said structure is self-centered with a position of said third region.  
     
     
       15. A structure as recited in  claim 13 , comprising: 
       said first, second and third active regions formed in a vertical stack;  
       said stack having a vertical axis passing through a center of said first, second and third active regions; and  
       said first, second and third active regions each being symmetric about said vertical axis.  
     
     
       16. A structure as recited in  claim 15 , wherein: 
       said first and second contacts being symmetric about said vertical axis.  
     
     
       17. A structure as recited in  claim 16 , comprising: 
       said third contact being symmetric about said vertical axis.  
     
     
       18. A structure as recited in  claim 13 , comprising: 
       said third active region having a ledge; and  
       said third contact disposed on said ledge.  
     
     
       19. A structure as recited in  claim 13 , comprising: 
       said third active region having ledges on opposing surfaces; and  
       said third contact disposed on each of said ledges.  
     
     
       20. A structure as recited in  claim 13 , comprising: 
       said third active region having a side surface and a plane surface; and  
       said third contact disposed on said side and plane surfaces.  
     
     
       21. A structure as recited in  claim 13 , comprising: 
       said third active region having a side surface and two opposing plane surfaces; and  
       said third contact disposed on each of said side and said opposing plane surfaces.  
     
     
       22. A structure as recited in  claim 13 , comprising: 
       said first active region having a width substantially equal to a width of said first contact; and  
       said second active region having a width substantially equal to a width of said second contact.  
     
     
       23. A structure as recited in  claim 13 , wherein: 
       said first active region comprises an emitter region;  
       said second active region comprises a collector region; and  
       said third active region comprises a base region.  
     
     
       24. A structure as recited in  claim 23 , wherein: 
       a position of said emitter region in said structure is self-centered with a position of said base region; and  
       a position of said collector region in said structure is self-centered with a position of said base region.  
     
     
       25. A structure as recited in  claim 23 , comprising: 
       said emitter, base and collector regions formed in a vertical stack;  
       said stack having a vertical axis passing through a center of said emitter, base, and collector regions; and  
       said emitter, base, and collector regions each being symmetric about said vertical axis.  
     
     
       26. A structure as recited in  claim 25 , wherein: 
       said first and second contacts being symmetric about said vertical axis.  
     
     
       27. A structure as recited in  claim 25 , comprising: 
       said third contact being symmetric about said vertical axis.  
     
     
       28. A structure as recited in  claim 23 , comprising: 
       said base region having a ledge; and  
       said third contact disposed on said ledge.  
     
     
       29. A structure as recited in  claim 23 , comprising: 
       said base region having ledges on opposing surfaces; and  
       said third contact disposed on each of said ledges.  
     
     
       30. A structure as recited in  claim 23 , comprising: 
       said base region having a side surface and a plane surface; and  
       said third contact disposed on said side and plane surfaces.  
     
     
       31. A structure as recited in  claim 13 , comprising: 
       said base region having a side surface and two opposing plane surfaces; and  
       said third contact disposed on each of said side and said opposing plane surfaces.  
     
     
       32. A structure as recited in  claim 23 , comprising: 
       said emitter region having a width substantially equal to a width of said first contact; and  
       said collector region having a width substantially equal to a width of said second contact.  
     
     
       33. A device as recited in  claim 1 , comprising: 
       said first and second active regions being symmetrically self-aligned.  
     
     
       34. A device as recited in  claim 1 , comprising: 
       said third contact formed on said third active region interior to an outer edge of third active region.  
     
     
       35. A structure as recited in  claim 13 , comprising: 
       a position of said first active region being self-centered with a position of said second active region in said device structure.  
     
     
       36. A structure as recited in  claim 13 , comprising: 
       said third contact formed on said third active region interior to an outer edge of third active region.